The present invention relates to a new and improved construction of a heat exchanger, especially a recuperator for high temperature reactors. Generally speaking, the heat exchanger of the present invention is of the type comprising a prismatic extending jacket or shell and a multiplicity of elongated hexagonal elements arranged internally of the jacket and essentially parallel to its primary direction i.e., its main direction of extent. Each hexagonal element comprises a central tube or pipe and extending thereabout heat transfer surfaces which extend to the outline or contour of the related hexagonal element, these heat transfer surfaces being connected at both ends with collectors seated at the central tube of the corresponding hexagonal element.
There have already been proposed heat exchangers wherein the hexagonal elements are assembled into a bundle or nest and retained by means of bands or straps or equivalent structure. What is disadvantageous with this construction is that during installation of the heat exchanger into its jacket or shell, which for instance, is accomodated in a blind hole of a concrete pressure tank, localized wide gaps can form during the different operating conditions, owing on the one hand to the different elongation of the bundle of hexagonal elements, and, on the other hand, the jacket or shell. The medium then can undesiredly escape through such wide gaps into a shunt or neighboring pass without having undergone any satisfactory heat exchange.
It is possible to apply tubular-shaped sleeves having sliding seals, sealing strips and so forth to the hexagonal elements in order to avoid the formation of such gaps or to seal such gaps if formed. Yet, the use of such sleeves is however associated with appreciable drawbacks as concerns the space requirements and the material requirements, and furthermore, complications arise owing to the fact that those locations where such sleeves are mounted are only accessable with difficulty and cannot be readily inspected.